This soreness is known as delayed-onset muscle soreness (DOMS) and normally appears 24-48 hours after strenuous or unaccustomed exercise. You might also notice a loss of range of motion in the joints of the affected limb(s). Even if you have been training for years, when we add new exercises in or change the structure of the session, this is unaccustomed to your muscles and so may lead to DOMS.
DOMS is not something to worry about and is perfectly safe. The good news is that when you do the same workout a second time you are not likely to experience the same level of soreness, so don’t let that first bout put you off!
Over the years many explanations have been given for DOMS, including a buildup of lactic acid, muscle spasms, inflammation, and micro tears of muscle and connective tissue. There is a lot of research for and against different explanations, and at the moment there isn’t a certain answer – it may well be a combination of a few factors. Eccentric contractions have been found to increase the risk of developing DOMS, so you may find you are more sore after doing eccentric pull ups (jumping up and lowering down) or push ups (lowering down to the floor).
Just like there are lots of explanations given for what DOMS is caused by, there are lots of myths about what can be done to treat or lessen it. Many think massages can help, but there is no concrete evidence behind this. Equally Epsom salts and stretching (before or after exercise) have little evidence proving that they relieve DOMS, and more evidence that they do nothing to help. There are a few things that show some promise, but again are no where near proven as a treatment. These include vitamin D, curcumin, and heat (which is why you may feel better after an Epsom salt bath). All this being said, if something makes you feel more comfortable then DO IT! It doesn’t matter if it’s not a scientifically proven treatment for DOMS, it may relieve other symptoms that are bothering you and that’s great too.
In summary, DOMS is something that is you are pretty much guaranteed to experience at some point in your training, and as annoying as it can be, it is just something you have to get on with! Just remember, the next time you train that session you shouldn’t have that same painful reaction, so don’t shy away from that session.